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5.1.29 eval
Syntax:
eval ( expression )
Type:
- none
Purpose:
- evaluates (quoted) expressions. Within a quoted expression, the
quote can be "undone" by an
eval (i.e., each eval "undoes" the
effect of exactly one quote). Used only when receiving a quoted expression
from an ssi link,
with quote and write to
prevent local evaluations when writing to an ssi link.
Example:
| link l="ssi:w example.ssi";
ring r=0,(x,y,z),ds;
ideal i=maxideal(3);
ideal j=x7+x3,x2,z;
// compute i+j before writing, but not std
// this writes 'std(ideal(x3,...,z))'
write (l, quote(std(eval(i+j))));
option(prot);
close(l);
// now read it in again and evaluate
// read(l) forces to compute 'std(ideal(x3,...,z))'
read(l);
==> _[1]=z
==> _[2]=x2
==> _[3]=xy2
==> _[4]=y3
close(l);
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See
Ssi links;
quote;
write.
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